Hydrocarbons in the form of petroleum deposits and crude oil reservoirs are distributed worldwide. These oil reservoirs are measured in the hundreds of billions of recoverable barrels. Because heavy crude oil has a relatively high viscosity and may adhere to surfaces, it is essentially immobile and cannot be easily recovered by conventional primary and secondary means.
Use of surface active agents or surfactants to increase solubility of oil through reduction in surface and interfacial tensions is another technique for increasing crude oil recovery. A wide variety of surfactants identified thus far are able to significantly reduce surface and interfacial tensions at oil/water and air/water interfaces. Because surfactants partition at oil/water interfaces, they are capable of increasing the solubility and bioavailability of hydrocarbons (Desai and Banat (1997) Microbiol. Mol. Biol. Rev. 61: 47-64; Banat (1995) Bioresource Technol. 51:1-12; Kukukina et al. (2005) Environment International 31:155-161; Mulligan (2005) Environmental Pollution 133:183-198). For example, Doong and Lei ((2003) Journal of Hazardous Materials B96:15-27) found that the addition of surfactants to soil environments contaminated with polyaromatic hydrocarbons increased the mineralization rate of some hydrocarbons.
In oil reservoirs where Injection water, which is typically used for introduction of substances into the oil reservoir, and the oil reservoir itself have high salt content, the high salt concentration may affect success of an oil release agent. The numbers of propylene oxide or ethylene oxide groups in a surfactant were each shown to affect the optimum salinity and solubilization ratio, in opposite direction (Yang et al. (2010) SPE129978, Society of Petroleum Engineers Improved Oil Recovery Symposium April 24-28). An increase in the number of ethoxy groups or decrease in the carbon chain length for alcohol ethoxylates increases the aqueous stability and optimum salinity of these compounds when used as co-solvents for oil recovery (Sahni et al. (2010) SPE 130007 Society of Petroleum Engineers Improved Oil Recovery Symposium April 24-28). There remains a need for additional chemical compounds that are biodegradable and have low toxicity, which may be used to release oil from hydrocarbon coated surfaces for improving oil recovery.